Telephone-exchange system



Dcr. 21. 1924. 1,512,584-

B. csf.- DUNHAM TELEPHONE EXCHANGE 'SYSTEM Filed-May 'z'o 1919 000il 000C' COOL.

by ffy,

Patented Oct. 21, 1924.

UNITED STATES PATENT OFFICE.

BERT G. DUNHAIM', OF HAWTHORNE, NEW JERSEY, .ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 0F NEW YORK. N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application vilecl May 20, 1919.

To all 'whom t may concern Be it known that I, Bnn'r G. DUNHAM, a citizen of the United States, residing at Hawthorne, in the county of Passaic, State of New Jersey, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is aV full, clear, concise, and exact description.

This invention relates to improvements in telephone exchange systems and has particular reference to a switch therefor. y

An object of the invention is to provide a switch by means of which a connection may be established to a called line through im- .pulses transmitted from a calling substation and whereby the called subscriber may be signaled by an operation of the impulse sending device at said calling substation. l

Another object is to arrange the subscribers lines in groups and provide means whereby the switch, in response to sets of impulses, may be moved over terminals of said groups in such manner that only impulses transmitted after those corresponding to the units digit of the wanted line will be effective to connect the signaling source to said line.

The inventiveidea involved is capable of receiving a variety of expressions one of which, for the purpose of illustrating the invention, is shown inthe accompanying drawing; but it is to be expressly understood that said drawing is employed merely for the purpose of facilitating the description of the invention as a whole and not to define the limits thereof, reference being had to the appended claims for this purpose. Y

The drawing is a diagrammatic view of a line switch circuit arranged in accordance with the invention.

In carrying out the invention, which is more particularly designed for use in -small private branch exchanges, the subscribers lines are preferably arranged in groups. A switch is provided for each line and upon the initiation of a call into the first group the subscribers switch is stepped, in response to the manipulation of his impulse sending device, onto the terminals in said group which are individual to the called line. At the termination of the first set of impulses a condition is effected at the switch whereby another series of impulses may be Serial No. 298,367.

transmitted which will not step the switch but will operate to connect the source of ringing current to the called line. If the wanted subscriber is in the second or third group, one or two sets of ten impulses each are transmitted which will move the brushes of the switch over the first or the first and second groups of terminals. At the end of each set of ten impulses the brushes will engage terminals which will only have the eiect of again causing the brushes to be stepped onto the first terminals of the succeeding group in response to the first impulse of a set corresponding to the units digit of the wanted line. When the terminals of the called line are reached, the calling subscriber then manipulates his impulse sending device in response to which the switch operates to connect the source of ringing current to the called line.

It is thought that the invention will be fully understood from the following detailed description of the operation in establishing a connection.

Referring to the drawing, when a calling subscriber removes his receiver from its switchhook to initiate a call, line relay l of the switch individual to the calling line will be energized over a circuit extending from grounded battery, right winding of relay l, back contact and armature of slow-to-release relay 2, substation apparatus and left winding of relay l to ground. Relay l, upon energizing, closes a circuit for slow-to-release relay 3 extending from grounded battery, winning of said relay, front contact and armature of relay l to ground. Relay 3 enei'gizes and connects the busy tone apparatus BZ through the alternate contact and left armature of relay 3 to terminal l so that should another subscriber operate his switch to engage a brush thereof with terminal t, a busy tone will be applied to his line.

The calling subscriber may now operate his impulse sending device 5 to transmit impulses in accordance with the number of the wanted line and in response to the first iinpulse, the line relay l retracts its armature and closes a circuit for stepping magnet 6 traceable from grounded battery, winding of said magnet, conductor 7, brush 8 which is `in itsnorinal position and in engagement with the first contact in the first group, back contact and right armature of the marginal slow-to-release relay 9, front contact and right armature of relay 3, winding yof relay 9, back contact and Varmature of relay 1 to ground. Magnet 6 operates to step the brushes of the switch onto the second row of terminals in the first group and relay 9 is energized in series with said magnet. Relays 3 and 9 being slow-to-release, remain energized during the transmission of impulses. By attracting its left armature, relay 9 establishes an ,energizing and hold- 4ing circuit for cutoit relay 10 extending from grounded battery, lower winding ot relay 10, Aalternate contact and left armature of relay 9 to ground. Relay 1() energizes and its two uppermost armatures disconnect the calling line during the transmission of impulses. In response to the second decnergization ol2 relay 1 when the second impulse is transmitted, magnet 6 is energized'over a circuit extending from grounded battery, winding of said magnet, front contact and right armature of relay 9, front contact and right armature of relay 3, winding of relay 9, back contact and armature of relay 1 to ground. Assuming that. the called line is located in the terminals of the Vfirst group,

stepping magnet@ continues to operate the switch in response to the impulses transmitted until the brushes of the switch engage the particular terminals individual to tlie called line. At the' termination of the iinpulses relay 9, after an interval, ,deenergizes If the called line is busy, a locking circuit will be established for cutoii relay 10 at the switch of the calling subscriber, which circuit extends from grounded battery, lower winding of `relay 10, alternate contact 11, contact 12, said` contacts 11 and 12 being closed before the circuit through the left armature of relay 9 is broken, front contact and lower armature of relay 10, brush 13, terminal t of the called line, left armature and alternate contact of relay 3 of the switch individual Ato the called line to ground through the busy tone apparatus. This vbusy tone is induced from the lower winding of relay 10 at the switch of the calling subseriber into the upper winding of said relay and fromV thence through Athe inner upper armature and front contact ot relay 10, con` denser 14, back contact and armature of relay 2, the calling subscribers substation apparatus and left winding of relay 1 to ground. The calling subscriber hearing this busy tone, replaces his receiver upon its switchhook 'and thusopens the circuit for line relay 1 which deenergizes. After an interval of time, relay 3 deenergizes and disconnects the busy tone apparatus. A selfinterrupting circuit is then established for stepping magnet 6 extending from grounded battery, right armature and back contact of magnet 6, brush 15, conductor 16, back contact and right armature of relay 3, winding of relay 9, back contact and armature of relay 1 to ground. Magnet (i operates to step the brushes of the switch until the same engage the normal terminals of the switch, whereupon the circuit is broken and said brushes will come to rest. Relay 9 and consequently relay 10 are both energized due to this self-interrupting stepping circuit but have no effect upon the return of the switch to its normal position, said relays releasing when the switch arrives at this position.

Assuming now that the called line is idle, relay 9 of the calling subscribers switch rcleases after the termination of the set ol iinpulses and breaks the circuit for cutolf relay 10. Upon the return of the impulse sending device at the calling substation to its normal position, the calling subscriber uguiu manipulates the same to interrupt. the circuit of the line relay 1 as before. The lirst retraction of the armature of relay 1 establishes a circuit for relay 2 at the called subscribers substation extending from grounded battery, winding ot said relay 2, brush 8 of the calling subscribers switcli, back contact and right armature of relay 9, said relay having released at the termination. of the first series of impulses, front contact and right armature of relay 3, winding of relay 9, back contact and armature of relay 1 to ground. Relay 2 of the called subscribers switch energizes in this circuit but relay 9 of the calling subscribe'."s switch, being marginal, does not energize in series with said rela-y 2. By attracting its annature, ringing current is applied to the called subscribers line extending from the source of ringing current, front contact and urina ture of relay 2, the called subscribers substation apparatus and left winding of line relay 1 of the called subscribers switch to ground. Said relay 1 energizes in this eircuit and thereby establishes a. circuit for the slow-to-release relay 8 which will connect the busy tone apparatus to the terminal 4 of the called subscribers switch to signal any other calling subscriber that the called subscriber is busy. Relay 2 of the called subscribcl"s switch being slow-to-release will .not (le-- energize during the vibration of the armature of the line relay at the calling subscribefs switch. The ailing subscriber may continue to operate his impulse sending device until the called subscriber responds. Upon the return of the impulse sending device to normal and the cessation of the transmission of fui-ther impulses, the line relay 1 of the calle ing subscribers switch will maintain its armature attracted and thus cause the release oi relay 2 at (he called subscribers switch which results in the ringing tone being disconnected. Conversation may now proceed between the calling and called subscribers. At the termination thereof the calling subscriber, by replacing his receiver upon its switchhook, causes the release ol his fifi lll() switch as previously described. When the called subscriber replacesI his receiver the line relay of his switch deenergizes and in turn causes the release of relay 3, whereupon the parts are again in normal position.

If the called subscribers line is in the second group of terminals of the calling subscribers switch, the impulse sending device 5 is lirst manipulated to transmit ten impulses in response to which the stepping magnet 6 is operated to pass the brushes of the switch over the terminals of the first group and onto a. set of terminals including a special contact 17. Upon the return of the impulse sending device to normal, the calling subscriber again operates the same to transmit the number of impulses corresponding to the unit digit of the called line. In response to the rst impulse, a circuit for stepping magnet 6 is closed which extends from grounded battery, winding of said magnet, conductor 7, contact 17, brush 8, back contact and right armature of relay 9, front contact and rifght armature of relay 3, winding of relay 9, back contact and armature of relay 1 to ground. Magnet 6 operates to step the brushes of the switch off of the special set of terminals and in response to further impulses the brushes of the switch are operated as previously described until the terminals individual t-o the called line are reached. The remainder of the operation in establishing the connection is as previously set forth. If the called line is in the third group of terminals the calling subscriber operates his impulse sendino' device totransmit two sets of ten impulses each, which will engage the brushes of his switch with the terminals including special contact 18 after which the operation is the same as previously described.

What is claimed is:

1. In a telephone exchange system, a calling line, a switch for extending said line, a terminal bank for said switch having its terminals arranged in groups, called lines connected to certain of said terminals, means for moving said switch over terminals of said groups in selecting a called line, means actuated in response to an operation of said moving means for connecting a signaling current to one of said called lines, and means including certain other terminals of said bank for preventing operation of the last named means until the switch has been connected to the called line.

2. In a telephone exchange system, a calling line, a switch for extending said line, a terminal bank for said switch having its terminals arranged in groups, called lines connected to certain of said terminals, a variably operable impulse sending device for moving said switch over the terminals of said groups in selecting a called line, means actuated in response to an operation of said impulse sending device for connecting a signaling current to one of said lines, and means including certain other terminals of said bank for preventing operation of the last named means until the switch has been connected to a called line.

3. In a telephone exchange system, a calling line, a switch for extending said line, a bank for said switch having its terminals arranged in groups, called lines connected to certain of said terminals, a variably operable impulse sending device, a controlling circuit including a marginal relay responsive to said impulse sending device for moving said switch, and a relay actuated in series with said marginal relay in response to an operation of said impulse sending device to connect a signaling current to one of said called lines.

4;. In a telephone exchange system, a calling line, a switch for extending said line, a bank for said switch having its terminals arranged in groups, called lines connected to certain of said terminals, a variably operable impulse sending device, a controlling circuit including a marginal relay responsive to said impulse sending device for moving said switch, a relay actuated in series with said marginal relay in response to an operation of said impulse sending device to connect a signaling current to one of said called lines, and means including certain other terminals of said bank for preventing operation of the second mentioned relay until the switch is connected to a called line.

5. In a telephone exchange system. a calling line, called lines arranged in groups. a switch for connecting said calling line to any one of said called lines, variably operable means for transmitting series of impulses to move said switch over the terminals of said groups of called lines, means actuated in response to an operation oi said variably operable means for connecting a signaling current to one of said called lines, and means operative when more than one series of impulses are transmitted for preventing actuation of the last named means until the switch has been moved over more than one of said groups of terminals.

In witness whereof, I hereunto subscribe my name this 15th day of May, A. D. 1919.

BERT G. DUNHAM. 

